Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnlyHint annotation, the description discloses meaningful behavioral details: derivation from business-card RegistrationDate or first-seen, the handling of unknown/seed tail (reported only in coverage, never bucketed), and keyless-cacheability. It adds significant context without contradicting annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and well-structured, with the title line followed by a brief explanation. The reference to 'issue #222' is somewhat extraneous, but the rest is informative and to the point.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has one optional parameter and no output schema, the description provides solid context: what the curve represents, the join date derivation logic, coverage categories, and the unknown tail behavior. It is sufficiently complete for an agent to select and invoke correctly, though it stops short of specifying the exact response shape.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for the single 'bucket' parameter, including its enum, default, and description. The tool description does not add additional parameter context beyond the schema, which is sufficient.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly identifies the tool as returning a 'Network joiners curve' with joiner counts bucketed by derived join date. It distinguishes from sibling tools by calling it 'The real onboarding curve' and specifying whole-network coverage split, making it distinct from related participant/network tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for onboarding/joiner analysis with a coverage split, but it does not explicitly state when to use this over siblings or provide exclusions. The context suggests it's the go-to for joiners curves, but no direct alternatives are named.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.